1. Legacy Satellite Systems
COMSTAR
TELSTAR
WESTAR
GALAXY
SATCOM ANIK
FDMA Analog Transponder architecture
SSB/FDM
FDM/FM

2. (Advanced Communications Technology Satellite)
NASA ACTS
(Advanced Communications Technology Satellite)
Deployed 1992
3 Fixed beam Antennas (East and West coasts)
2 Spot beam antennas (Topeka, Cheyenne Wells)
Baseband processing (Spot Beams)
Straight up-conversion (2 Fixed Beams - one fixed Beam switchable)
CONUS coverage
Multibeam Antennas
Rx – Ghz
Tx – Ghz
110 M-Baud (w/o FEC)
55 M-Baud (64 bit frame, Rate ½, length 5 Convolutional FEC)

3. Geosynchronous Sats 22,300 mi altitude 2 degree spacing C band 6/4 Ghz
Ku band 14/12 Ghz
Typical C band parameters
500 Mhz total BW
12 Transponders using 36 Mhz /4 Mhz guardbands
Additional 12 transponders using polarization diversity/20 Mhz offsets
Transponder Usage
FDMA: Part of transponder bandwidth is leased by customer for continuous use.
Analog/Digital
TDMA: Entire bandwidth of transponder is leased for allocated time slots
Usually digital only
Timing is critical due to range from different ground stations
CDMA:

4. CDMA (Code division Multiple Access)
Spread Spectrum fPR + +
NRZ fI
Recovered NRZ fI IF
A and B are identical and synchronized
Pseudo Random Sequence Generator A
@fPR >> fI
Pseudo Random Sequence Generator B
@fPR >> fI